Association of Long-Term Diet Quality with Hippocampal Volume: Longitudinal Cohort Study

Abstract

Background: Diet quality is associated with brain aging outcomes. However, few studies have explored in humans the brain structures potentially affected by long-term diet quality. We examined whether cumulative average of the Alternative Healthy Eating Index 2010 (AHEI-2010) score during adult life (an 11-year exposure period) is associated with hippocampal volume.

Methods: Analyses were based on data from 459 participants of the Whitehall II imaging sub-study (mean age [standard deviation] (SD) = 59.6 [5.3] years in 2002-2004, 19.2% women). Multimodal magnetic resonance imaging examination was performed at the end of follow-up (2015-2016). Structural images were acquired using a high-resolution 3-dimensional T1-weighted sequence and processed with Functional Magnetic Resonance Imaging of the Brain Software Library (FSL) tools. An automated model-based segmentation and registration tool was applied to extract hippocampal volumes.

Results: Higher AHEI-2010 cumulative average score (reflecting long-term healthy diet quality) was associated with a larger total hippocampal volume. For each 1 SD (SD = 8.7 points) increment in AHEI-2010 score, an increase of 92.5 mm³ (standard error = 42.0 mm³) in total hippocampal volume was observed. This association was independent of sociodemographic factors, smoking habits, physical activity, cardiometabolic health factors, cognitive impairment, and depressive symptoms, and was more pronounced in the left hippocampus than in the right hippocampus. Of the AHEI-2010 components, no or light alcohol consumption was independently associated with larger hippocampal volume.

Conclusions: Higher long-term AHEI-2010 scores were associated with larger hippocampal volume. Accounting for the importance of hippocampal structures in several neuropsychiatric diseases, our findings reaffirm the need to consider adherence to healthy dietary recommendation in multi-interventional programs to promote healthy brain aging.

Keywords: Alternative Healthy Eating Index; Dietary indices; Hippocampal volume; Older adults; Prospective study.

Figure 1

Association between cumulative average of Alternative Healthy Eating Index 2010 over 11-year exposure period (1991–1993–2002–2004) and hippocampal volumes. M1: Model adjusted for age, sex, and total energy intake. M2: M1+ occupational grade, ethnicity, smoking habits, physical activity, cardiometabolic factors, including body mass index, antecedent of coronary heart diseases, hypertension, type II diabetes, and dyslipidemia. M3: M2 + depressive symptoms and cognitive deficit. Hippocampal volumes were normalized using the formula Voladj = vol – b × (intracranial volume – mean intracranial volume ), where b is the regression coefficient of hippocampal volume on intracranial volume, and subsequently scaled to standard deviation units by computing z score.

Figure 2

Association between Alternative Healthy Eating Index 2010 (AHEI-2010) component scores and hippocampal volumes. Separate linear regression models were performed, in which each cumulative average of AHEI-2010 component score was included. All component AHEI-2010 scores were standardized by using z-scores (mean = 0, standard deviation = 1). Models were adjusted for age, sex, total energy intake, occupational grade, ethnicity, smoking habits, physical activity, cardiometabolic factors, including body mass index, antecedent of coronary heart diseases, hypertension, type II diabetes, dyslipidemia, depressive symptoms, and cognitive deficit. Hippocampal volume was normalized using the formula Voladj = vol – b × (intracranial volume – mean intracranial volume), where b is the regression coefficient of hippocampal volume on ICV and subsequently scaled to standard deviation units by computing the z-score. P < .05 P ≥ .05.

Supplementary Figure 1

Flow chart diagram mapping the selection of participants.

Supplementary Figure 2

Association between modified AHEI-2010 scores and hippocampal volume.